The purification and properties of bovine thymosin have been described by Hooper et al, Annals New York Academy of Sciences, Vol. 249 p. 125-144 (1975). A process of preparing thymosin has also been described in British Pat. No. 1,195,980.
A crude thymosin which is referred to as "thymosin-fraction 3" is described by Hooper et al.
Thymosin-fraction 3 is a prime intermediate in the preparation of pure thymosin from calf thymus glands. Thymosin-fraction 3 contains all the thymosin originally present in the calf thymus glands but contains only 1% of the original weight of the glands. The greatly reduced bulk and the 100-fold purification allows the application of known and usual protein-purification procedures for the preparation of pure thymosin.
Purified thymosin is known to consist of several proteins with molecular weights ranging from 1,200-14,000. It has been shown to stimulate lymphoid tissue proliferation and to thereby increase immunity to infectious processes. Recent clinical trials involving immunodeficiency diseases have shown that thymosin increases the number of peripheral blood T-cells thereby partially restoring immunological competence.
Previous methods of extracting thymosin from thymus glands involved homogenizing the glands in saline solution and centrifuging the homogenate. Such processes are laborious for the extraction of large quantities (500-1,000 pounds) of thymus glands and result in the extraction of undesirable fatty constituents of the glands which interfere with subsequent processing. In the published procedures the heat-labile proteins in the saline extract are precipitated by heating the extract to 80.degree. C. in a water bath. In previous procedures, the extract obtained after removing the heat-labile proteins is mixed directly with five or ten volumes of cold acetone to precipitate thymosin-fraction 3.